Method of delivering a stent

ABSTRACT

The invention is directed to a stent delivery method and system which generally includes an elongated delivery sheath and a catheter disposed within an outer lumen of the sheath having an expandable member on its distal extremity. An expandable stent is mounted on the expandable member of the catheter. The distal portion of the sheath tapers down and is tucked within an elastic cone during transport of the stent to a stenotic region. A manipulating device is provided on the proximal end of the delivery system to effect relative axial movement between the sheath and the catheter so as to expose the stent mounted on the expandable member on the catheter within a body lumen such as a coronary artery and allow the expansion of the stent by the expansion of the expandable member. The elastic cone thereby disengages from the sheath and collapses about the distal end of the catheter. The delivery sheath has a first port in its distal end and a second port in the sheath wall proximally disposed from the distal end of the sheath. The catheter likewise has a first port in its distal end and a second port proximally disposed from the distal end of the catheter. An inner lumen extends within the distal portion of the catheter between the first and second ports and slidably receives a guiding member such as a guidewire. This system allows the stent to be delivered over a guidewire previously advanced to the desired location within a body lumen.

This application is a divisional of U.S. Ser. No. 08/630,528 filed Apr.10, 1996, which issued as U.S. Pat. No. 5,782,855 on Jul. 21, 1998,which is a divisional application of U.S. Ser. No. 08/085,959 filed Jul.6, 1993 which issued as U.S. Pat. No. 5,507,768 on Jul. 6, 1993 andwhich is a continuation-in-part application of U.S. Ser. No. 07/647,464filed on Jan. 28, 1991, which is now abandoned.

BACKGROUND OF THE INVENTION

This invention relates to devices for the treatment of heart disease andparticularly to endo-arterial prosthesis, which are commonly calledstents.

Several interventional treatment modalities are presently used for heartdisease including balloon and laser angioplasty, atherectomy and by-passsurgery.

In typical balloon angioplasty procedures, a guiding catheter having apreformed distal tip is percutaneously introduced through the femoralartery into the cardiovascular system of a patient in a conventionalSeldinger technique and advanced within the cardiovascular system untilthe distal tip of the guiding catheter is seated in the ostium of adesired coronary artery. A guidewire is positioned within an inner lumenof a dilatation catheter and then both are advanced through the guidingcatheter to the distal end thereof. The guidewire is first advanced outof the distal end of the guiding catheter into the patient's coronaryvasculature until the distal end of the guidewire crosses a lesion to bedilated, then the dilatation catheter having an inflatable balloon onthe distal portion thereof is advanced into the patient's coronaryanatomy over the previously introduced guidewire until the balloon ofthe dilatation catheter is properly positioned across the lesion. Oncein position across the lesion, the balloon which is made of relativelyinelastic materials, is inflated to a predetermined size with radiopaqueliquid at relatively high pressure (e.g., greater than 4 atmospheres) tocompress the arteriosclerotic plaque of the lesion against the inside ofthe artery wall and to otherwise expand the inner lumen of the artery.The balloon is then deflated so that blood flow can be resumed throughthe dilated artery and the dilatation catheter can be removed therefrom.Further details of dilatation catheters, guidewires, and devicesassociated therewith for angioplasty procedures can be found in U.S.Pat. No. 4,323,071 (Simpson-Robert); U.S. Pat. No. 4,439,185(Lindquist); U.S. Pat. No. 4,516,972 (Samson); U.S. Pat. No. 4,538,622(Samson, et al.); U.S. Pat. No. 4,554,929 (Samson, et al.); U.S. Pat.No. 4,616,652 (Simpson); U.S. Pat. No. 4,638,805 (Powell); and U.S. Pat.No. 4,748,982 (Horzewski, et al.) which are hereby incorporated hereinin their entirety by reference thereto.

A major problem which can occur during balloon angioplasty procedures isthe formation of intimal flaps which can collapse and occlude the arterywhen the balloon is deflated at the end of the angioplasty procedure.Another major problem characteristic of balloon angioplasty proceduresis the large number of patients which are subject to restenosis in thetreated artery. In the case of restenosis, the treated artery may againbe subjected to balloon angioplasty or to other treatments such asby-pass surgery, if additional balloon angioplasty procedures are notwarranted. However, in the event of a partial or total occlusion of acoronary artery by the collapse of a dissected arterial lining after theballoon is deflated, the patient is put in an extremely dangeroussituation requiring immediate medical attention, particularly in thecoronary arteries.

A major focus of recent development work in the treatment of heartdisease has been directed to endoprosthetic devices called stents.Stents are generally cylindrically shaped intravascular devices whichare placed within a damaged artery to hold it open. The device can beused to prevent restenosis and to maintain the patency of blood vesselimmediately after intravascular treatments. In some circumstances, theycan also be used as the primary treatment device where they are expandedto dilate a stenosis and then left in place.

However, the rapid and effective delivery of a stent to the desirelocation within the patient's vasculature has been found to bedifficult, particularly in those situations in which an intimal flap hasoccluded an artery. Attempts to advance a stent into regions of coronaryarteries occluded by dissected arterial linings have not been verysuccessful.

The two basic methods and systems have been developed for deliveringstents to desired locations within body lumens. One method and systeminvolves compressing or otherwise reducing the diameter of an expandablestent, disposing the compressed stent within a lumen provided in thedistal end of a tubular catheter, advancing the catheter through thepatient's vasculature until the distal end of the catheter isimmediately adjacent to the desired vascular location and then pushingthe stent out the distal end of the catheter into the desired location.Once out of the catheter, the compressed stent expands or is expanded tothereby hold open the artery or other body lumen into which it isplaced.

Another method and system involves disposing a compressed or otherwisesmall diameter stent about an expandable member such as a balloon on thedistal end of a catheter, advancing the catheter through the patient'svascular system until the sent is in the desired location within a bloodvessel and then expanding the expandable member on the catheter toexpand the stent within the blood vessel. The expanded expandable memberis then contracted and the catheter withdrawn, leaving the expandedstent within the blood vessel, holding open the passageway thereof.

The following references illustrate various types of stents and stentdelivery systems. The list is meant to be exemplary, not exhaustive onthe subject.

    ______________________________________                                        U.S. 3,868,956                                                                              U.S. 4,733,665                                                                           U.S. 4,856,516                                       U.S. 4,503,569                                                                              U.S. 4,760,849                                                                           U.S. 4,878,906                                       U.S. 4,512,338                                                                              U.S. 4,762,128                                                                           U.S. 4,886,062                                       U.S. 4,553,545                                                                              U.S. 4,768,507                                                                           U.S. 4,907,336                                       U.S. 4,560,374                                                                              U.S. 4,795,458                                                                           U.S. 4,913,141                                       U.S. 4,655,771                                                                              U.S. 4,800,882                                                                           U.S. 4,923,464                                       U.S. 4,665,918                                                                              U.S. 4,830,003                                                                           U.S. 4,950,227                                       ______________________________________                                    

What has been needed and heretofore unavailable is a stent deliverysystem which can be quickly and easily used in a wide variety ofsituations and particularly in emergency situations where a dissectedarterial lining has collapsed and has occluded the flow of blood to avital organ. The present invention satisfies this need.

SUMMARY OF THE INVENTION

This invention is directed to an improved stent delivery system whichcan quickly and easily position a stent into an occluded region of ablood vessel.

The stent delivery system of the invention includes an elongated sheathhaving an inner lumen extending therein, a distal portion which tapersdown, a first port in its distal end which is adapted to receive aguidewire and a second port spaced proximally from the distal end of thedelivery sheath which is also adapted to receive a guidewire, both ofthe ports being in fluid communication with the inner lumen of thesheath. The delivery system also includes an elastic cone with a smallaperture in its distal end and a large aperture in its proximal endwhich receives the distal end of the elongated sheath. In addition, thedelivery system includes an intravascular catheter slidably disposedwithin the delivery sheath. The catheter has an expandable member of thedistal extremity thereof, such as an inflatable balloon, which isadapted to receive an expandable stent on the exterior thereof. Thecatheter has a first port in its distal end adapted to receive aguidewire and a second port spaced proximally from the distal end of thecatheter adapted to receive a guidewire, with both of these ports beingin communication with an inner lumen extending within the interior ofthe catheter. The second guidewire receiving port should be spacedproximally from the expandable member on the distal extremity of thecatheter. Means may be provided to adjust the relative axial positionsof the catheter and sheath to expose the expandable stent on theexpandable member of the catheter so that the stent can be expandedagainst the blood vessel wall by expanding the expandable member.

Preferably, both the delivery sheath and the intravascular catheter haveslits in the walls, thereof which extend distally from their proximalports to facilitate the removal of these devices from the guidewire uponthe withdrawal of the delivery system from the patient's vascular systemafter the delivery of a stent. The distal end of the delivery sheath mayalso have slits in the walls thereof which extend a short distanceproximally from its distal end to facilitate in the relative axialposition adjustment of the delivery sheath and intravascular catheter.

In a typical situation, the guidewire used to deliver a dilatationcatheter through the patient's vascular system to a stenotic regiontherein is left disposed within the patient after the dilatationcatheter has been removed therefrom. To maintain access to the stenoticregion, the distal end of the guidewire should be left crossing thestenotic region where the stent is to be placed. The proximal end of theguidewire, which extends out of the patient, is first inserted throughan elastic cone by threading the guidewire into the smaller and out thelarger of the two apertures which comprise the cone. Then the guidewireis inserted through the port in the distal end of the intravascularcatheter which has a stent mounted on the expandable member. Theintravascular catheter is disposed within the delivery sheath with thedistal end of the catheter extending out the port in the distal end ofthe delivery sheath to facilitate the insertion of the proximal end ofthe guidewire. The relative axial position between the delivery sheathand intravascular catheter is adjusted so that the expandable member onthe distal extremity of the intravascular catheter with the expandablestent mounted thereon is pulled back into the inner lumen of thedelivery sheath. The distal end of the delivery sheath is then tuckedwithin the large aperture of the elastic cone. Tucking the deliverysheath within the elastic cone aids the advancement of the stentdelivery system through the patient's vascular system by providing thesystem with a profile suited for making turns through tortuous vessels.The delivery sheath and the catheter therein are then advanced throughthe patient's vascular system, preferably over a guidewire which extendsfrom outside the patient to the ostium of the desired coronary artery,until the stent mounted on the expandable member of the intravascularcatheter is positioned within the stenotic region of the patient's bloodvessel.

The relative axial positions of the delivery sheath and theintravascular catheter having the stent thereon is adjusted to urge thedistal end of the vascular catheter out of the distal end of the sheathto expose the expandable stent. Either the catheter can be advanceddistally with respect to the sheath or the sheath can be withdrawnproximally with respect to the catheter or both movements can beemployed. As the relative axial positions are adjusted, the conedisengages from the sheath and collapses upon the distal end of thecatheter. Once the stent is completely out of the delivery sheath, theexpandable member on the intravascular catheter can be expanded toexpand the stent against stenotic mass within the blood vessel. Afterexpanding the stent, the expandable member on the vascular catheter iscontracted so that the catheter can be removed from the patient's bloodvessel, leaving the expanded stent in its desired position therein.

The delivery sheath and the intravascular catheter may be withdrawntogether or the sheath may be withdrawn first followed by withdrawal ofthe catheter. The sheath and the catheter can be peeled away from theguidewire with the guidewire sliding through the slits which extenddistally from the proximal ports thereof. The exposed section of theguidewire is secured, e.g., manually held, in place so that the sheathand the intravascular catheter can be pulled off the proximal end of theguidewire.

The delivery system of the invention can effectively deliver a stent toa desired location within a patient's blood vessel, it can allow thestent to be secured within the desired location, and it can be easilyand quickly removed. These and other advantages of the invention willbecome more apparent from the following detailed description of theinvention, when taken in conjunction with the accompanying exemplarydrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a partial longitudinal cross-sectional view of a stentdelivery system which embodies features of the invention.

FIG. 2 is a top view of the delivery sheath and elastic cone of thestent delivery system shown in FIG. 1.

FIG. 3 is a transverse cross-sectional view taken along the lines 3--3shown in FIG. 1.

FIG. 4 is a transverse cross-sectional view taken along the lines 4--4shown in FIG. 1.

FIG. 5 illustrates a stent mounted on the outer surface of a balloon ofthe intravascular catheter shown in FIG. 1.

FIG. 6 illustrates the advancement of the stent delivery system shown inFIG. 5 into an artery which has been damaged by an intravascularprocedure such as an angioplasty and the location of the elastic coneprior to the relative axial position adjustment of the delivery sheathand intravascular catheter.

FIG. 7 illustrates the inflation of the balloon on the intravascularcatheter shown in FIG. 1 which expands the stent mounted on the exteriorthereof and the location of the elastic cone after the relative axialposition adjustment of the delivery sheath and intravascular catheter.

FIG. 8 illustrates the expanded stent disposed within a damaged arterialsection maintaining the patency thereof.

FIG. 9 is a partial cross-sectional view of the manipulator shown inFIG. 1.

FIG. 10 is a perspective view of an alternative manipulator mounted onthe proximal end of the delivery system shown in FIG. 1.

FIG. 11 is a plan view of the manipulator shown in FIG. 10.

FIG. 12 is an elevational view, partially in section, of the manipulatorshown in FIG. 10.

DETAILED DESCRIPTION OF THE INVENTION

FIGS. 1-4 illustrate a stent delivery system which embodies features ofthe invention. Generally, the delivery system includes a delivery sheath10 which has an outer lumen 11 and an intravascular catheter 12 disposedwithin the outer lumen 11. The intravascular catheter has an elongatedcatheter body 13 and a balloon 14 on the distal portion of the catheterbody. A manipulating device 15 is provided on the distal end of thedelivery system which is employed to effect relative axial orlongitudinal movement between the delivery sheath 10 and theintravascular catheter 12. An expandable stent 16, which is to bedelivered within a patient's body lumen, is mounted on the exterior ofthe balloon 14. During the advancement of the stent delivery systemthrough the patient's vascular system to the region of an occlusion, thesheath 10 is tucked within an elastic cone 58. FIG. 1 shows the locationof the elastic cone 58 after the relative axial positions of the sheath10 and catheter 12 are adjusted to expose the expandable stent 16.

The delivery sheath 10 has a distal port 17 in its distal end which isin fluid communication with the outer lumen 11 and a proximal port 18disposed proximally to the distal port. The distal portion of deliverysheath 10 tapers down in a spherical-like manner so that thecross-sectional area is somewhat less in the distal region than thecross-sectional area of the rest of the delivery sheath. A slit 19extends from the proximal port 18 to a location just proximal to thedistal port 17. In one embodiment, a plurality of slits 59 in the wallof sheath 10 extend a short distance from the distal port 17. Ascontemplated, the slits 59 would facilitate in the relative axialposition adjustment of the sheath 10 and intravascular catheter 12.

The intravascular catheter 12 has a distal port 20 and a proximal port21 which are in fluid communication with a first inner lumen 22extending within the distal portion of the catheter 12 and being adaptedto slidably receive a guidewire therein. A slit 23 extends from theproximal port 21 to a location 24 proximal to the proximal end ofballoon 14. The proximal end of the guidewire receiving first innerlumen 22 is provided with a ramp 25 to guide the proximal end ofguidewire 26 out the proximal port 21 of intravascular catheter 12 whenthe catheter is mounted onto the guidewire, as will be discussedhereinafter. A second, much longer inner lumen 27 is provided within thecatheter body 13 to direct inflation fluid from the proximal end of thecatheter body to the interior of the balloon 14.

Proximal to the proximal port 21 in the catheter body 13 is a stiffeningmember 28 which is disposed in third inner lumen 29 provided within thecatheter body 13. As shown in the drawings, the third inner lumen 29 andthe first inner lumen 22 may be the same lumen with a plug 30 separatingthe two lumens. The ramp 25 is on the distal side of the plug 30.

As illustrated in FIGS. 1 and 9, the manipulator 15 on the proximal endof the delivery system has a housing 31 with an interior chamber 32, acap 33 rotatably mounted onto the distal end of the housing 31, anelongated drive member 34 which has male threads on the exterior,thereof and which is at least partially disposed within the interiorchamber 32 and a Luer lock 35 which is fixed within the proximal end ofthe housing 31. The proximal end 36 of the sheath 10 is secured to thedistal end 37 of the elongated drive member 34 which extends out of thedistal end of the housing 31. As shown in more detail in FIG. 9, theproximal end 38 of the catheter body 13 passes through passageway 39 inthe elongated drive member 34 and is fixed within the Luer lock 35 bysuitable means such as adhesive. The cap 33 which is rotatably mountedonto the distal end of the housing 31 is provided with an inner threadedcollar 40 adapted to threadably engage the threaded exterior of theelongated driving member 34. Rotation of the cap 33 moves the drivingmember 34 axially to thereby effect relative axial movement between thesheath 10 and the intravascular catheter 12. As can be seen from FIGS. 1and 6, the outer lumen 11 is axially spaced from catheter 12, at innerlumen 27, in a substantially non-abutting manner. Thus when the deliverysheath 10 overlies the intravascular catheter 12, there is little or nocontact present at the interface between the outer lumen 27 proximal tothe distal end of intravascular catheter 12.

In a typical situation, the stent delivery system of the invention isused after an intravascular procedure has damaged a patient's arteriallining to such an extent that the lining needs support to prevent itfrom collapsing into the arterial passageway and thereby preventingsufficient blood flow through the blood vessel. In these situationsthere will usually be a guidewire 26 (or other guiding member) in placeextending across the damaged section of the artery such as shown in FIG.6. The proximal end of the guidewire 26, which extends out of thepatient during the entire procedure, is inserted through the elasticcone 58 by threading the guidewire 26 into the small aperture 61 and outthe large aperture 60 of the cone 58. The guidewire 26 is then insertedthrough the distal port 20 in the distal end of the catheter 12 andadvanced proximally through the first inner lumen 22 until the proximalend of the guidewire impacts the ramp 25 and is thereby directed throughthe proximal port 21.

The intravascular catheter 12 is preferably positioned within the outerlumen 11 of the delivery sheath 10 so that at least a significantportion of the proximal port 18 in the sheath is in alignment with theproximal port 21 of the intravascular catheter. In this manner, proximaladvancement of the guidewire 26 through the inner lumen 22 will alsodirect the proximal end of the guidewire out the proximal port 18 in thedelivery sheath 10. The sheath 10 is then tucked within the elastic cone58 by inserting the distal end of sheath 10 into the proximal end andlarge aperture 60 of the cone 58. The proximal end of the guidewire 26may then be manually held to maintain the position of the guidewirewithin the patient's vasculature, while the stent delivery system isadvanced over the guidewire and through the patient's vascular system.The function of the elastic cone 58 is to facilitate the advancement ofthe stent delivery system. By tucking the distal end of sheath 10 withinthe cone 58 as shown in FIG. 6, the stent delivery system has a profilesuited for successfully maneuvering about the sharp turns and angles ofthe patient's vasculature. The advancement of the stent delivery systemcontinues until the distal ends of the catheter and sheath extendadjacent to or across the damaged arterial site. Next, the manipulator15 on the proximal end of the delivery system is actuated by rotatingthe cap 33 on the proximal end of the housing 31 to move the sheath 10proximally with respect to the catheter 12 and thereby expose the stent16 mounted on the balloon 14. The elastic cone 58 thereby disengages thesheath 10 and collapses in engagement about the distal portion of thecatheter 12 as is shown in FIG. 1. When the balloon and the stentmounted thereon are properly placed within the damaged artery, inflationfluid is directed under substantial pressure through the Luer lock 35and the inflation lumen 27 in the catheter body 13 to the interior ofthe balloon 14, expanding the balloon and simultaneously expanding thestent 16 against the blood vessel wall as shown in FIG. 7. The deliverysystem, both the sheath 10 and the catheter 12, may then be removed fromthe patient along with the guidewire 26, leaving the expanded stent 16within the damaged arterial section as shown in FIG. 8 to maintain thepatency thereof.

The housing 31 of the manipulator 15 can be held in the palm of thephysician's hand, with the thumb and index finger thereof used to rotatecap 33 and thereby cause the necessary relative motion between thesheath 10 and intravascular catheter 12 to expose the stent 16 mountedon the balloon 14. The physician can operate an inflation device, suchas described in U.S. Pat. No. 4,439,185, with his or her free hand toinject inflation fluid through Luer lock 35 into the interior of theballoon 14 to inflate the balloon and thereby expand the stent 16 whileholding the delivery system in place with the other hand. Upon deflatingthe balloon 14, the manipulator 15 can again be actuated by thephysician rotating cap 33 with the fingers of the hand holding themanipulator 15, to cause relative rotation between the intravascularcatheter 12 and the sheath 10, to pull the intravascular catheter 12back into the distal end of the sheath 10 (or pushing the distal end ofthe sheath over the distal end of the intravascular catheter 12,depending upon the perspective). The entire assembly, including theguidewire 26, can then be removed from the patient.

The alternative manipulator 50 illustrated in FIGS. 10-12 generallyincludes a housing 51 with an interior chamber 52 and a slidable element53 with a depending portion 54 which extends through a slot 55 in thewall of the housing and is secured to the proximal end of the sheath 10which extends through an opening provided in the distal end of thehousing. The catheter 12 extends out the proximal end of the sheath 10,out an opening in the proximal end of the housing 51 and into a Luerlock 56 secured to the proximal end of the housing. The proximal end ofthe catheter 12 is secured within the Luer lock 56 to be in fluidcommunication with the inner inflation lumen 27 of the catheter so thatinflation fluid can be injected through the Luer lock to the interior ofthe balloon 14 on the catheter to expand the balloon and the stent 16mounted thereon. As is evident from FIG. 10, movement from element 53 onthe exterior of the housing 51 will effect the relative axial movementbetween the delivery sheath 10 and the catheter 12 required to exposethe stent 16 mounted on the balloon 14. The slot 55 has narrowedportions near both ends thereof which have widths just slightly smallerthan the depending element 54 so that the position of the slidableelement 53 can be locked. The underside of the housing 51 may beprovided with undulated surface 57 which is adapted to receive thefingers of an operator to facilitate the gripping thereof.

The dimensions of the intravascular catheter will generally follow thedimensions of intravascular catheters used in angioplasty procedures inthe same arterial location. Typically, the length of a catheter for usein the coronary arteries is about 150 cm, the outer diameter of thecatheter shaft is about 0.035 inch (0.89 mm), the length of the balloonis typically about 2 cm and the inflated diameter about 1 to about 8 mm.

The materials of construction may be selected from those used inconventional balloon angioplasty catheters, such as those described inthe patents incorporated by reference. The delivery sheath willgenerally be slightly shorter than the intravascular catheter, e.g., byabout the length of the manipulating device 15 or 50, with an innerdiameter large enough to accommodate the intravascular catheter and toallow the catheter free longitudinal movement therein. The sheath andthe catheter shaft can be made of conventional polyethylene tubing.

While the present invention has been described herein in terms ofdelivering an expandable stent to a desired location within a patient'sblood vessel, the delivery system can be employed to deliver stents tolocations within other body lumens such as urethra or Fallopian tubes sothat the stents can be expanded to maintain the patency of these bodylumens. Various changes and improvements may also be made to theinvention without departing from the scope thereof.

What is claimed is:
 1. A method of delivering an expandable stent to adesired location within a patient's body lumen which has a guide wiredisposed therein with a proximal end extending out of the patient, themethod comprising:providing an elongated sheath having proximal anddistal ends and a wall therebetween, a first port in the distal end ofthe sheath, a second port in the proximal end of the sheath and a sideport spaced proximally from the distal end; an elongated catheterdisposed within the elongated sheath having proximal and distal ends, afirst port in the distal end of the elongated catheter and a side portspaced proximally from the distal end of the elongated catheter, thecatheter having an expandable member proximally adjacent to the distalend of the catheter and having mounted on the exterior thereof anexpandable stent, the catheter having an inner lumen to slidably receivea guide wire therein; adjusting the relative axial positions of theelongated sheath and the catheter so as to at least partially align theside port of the elongated sheath and side port of the elongatedcatheter; positioning the guide wire so that a portion of the guide wireextends through the side port of the elongated sheath and side port ofthe elongated catheter; advancing the guide wire to the desired locationwithin the body lumen; advancing the sheath and the catheter over theguide wire through the body lumen to the desired location therein;adjusting the relative axial positions of the sheath with respect to thecatheter to expose the expandable stent on the expandable member;providing a slit in the sheath extending from the side port and thefirst port in the sheath distal end so that as the sheath is withdrawnproximally relative to the catheter the sheath slit is pealed away fromthe stationary guide wire; inflating the expandable member to therebyexpand the stent mounted thereon at the desired location within the bodylumen; after the expandable stent has been implanted, deflating theexpandable member on the catheter; and withdrawing the catheter and thesheath from the body lumen.
 2. The method of claim 1, providing a slitin the catheter extending from the side port to a location proximal ofthe expandable member, the catheter slit and sheath slit beingsubstantially axially aligned.
 3. The method of claim 2, wherein duringthe withdrawing step, the catheter slit and sheath slit are peeled awayfrom the stationary guide wire in a rapid exchange manner.
 4. The methodof claim 1, providing a tapered section from proximal to distal in atleast a distal portion of the sheath so that the catheter will moreeasily negotiate tortuous body lumens.